Quantitative Digital Subtraction Angiography Measurement of Arterial Velocity at Low Radiation Dose Rates.

PURPOSE: Quantitative digital subtraction angiography (qDSA) has been proposed to quantify blood velocity for monitoring treatment progress during blood flow altering interventions. The method requires high frame rate imaging [~ 30 frame per second (fps)] to capture temporal dynamics. This work investigates performance of qDSA in low radiation dose acquisitions to facilitate clinical translation. MATERIALS AND METHODS: Velocity quantification accuracy was evaluated at five radiation dose rates in vitro and in vivo. Angiographic technique ranged from 30 fps digital subtraction angiography ( 29.3 ± 1.7 mGy / s at the interventional reference point) down to a 30 fps protocol at 23% higher radiation dose per frame than fluoroscopy ( 1.1 ± 0.2 mGy / s ). The in vitro setup consisted of a 3D-printed model of a swine hepatic arterial tree connected to a pulsatile displacement pump. Five different flow rates (3.5-8.8 mL/s) were investigated in vitro. Angiography-based fluid velocity measurements were compared across dose rates using ANOVA and Bland-Altman analysis. The experiment was then repeated in a swine study (n = 4). RESULTS: Radiation dose rate reductions for the lowest dose protocol were 99% and 96% for the phantom and swine study, respectively. No significant difference was found between angiography-based velocity measurements at different dose rates in vitro or in vivo. Bland-Altman analysis found little bias for all lower-dose protocols (range: [- 0.1, 0.1] cm/s), with the widest limits of agreement ([- 3.3, 3.5] cm/s) occurring at the lowest dose protocol. CONCLUSIONS: This study demonstrates the feasibility of quantitative blood velocity measurements from angiographic images acquired at reduced radiation dose rates.

Variceal and Nonvariceal Upper Gastrointestinal Bleeding Refractory to Endoscopic Management: Indications and Role of Interventional Radiology.

For over 60 years, diagnostic and interventional radiology have been heavily involved in the evaluation and treatment of patients presenting with gastrointestinal bleeding. For patients who present with upper GI bleeding and have a contraindication to endoscopy or have an unsuccessful attempt at endoscopy for identifying or controlling the bleeding, interventional radiology is often consulted for evaluation and consideration of catheter-based intervention.

Quantification of Iliac Arterial Blood Velocity in Stenotic Phantom and Porcine Models Using Quantitative Digital Subtraction Angiography.

PURPOSE: To assess the feasibility of using quantitative digital subtraction angiography (qDSA) to quantify arterial velocity in phantom and porcine stenotic iliac artery models. MATERIALS AND METHODS: Varying stenoses (mild, <50%; moderate, 50%-70%; and severe, >70%) were created in a silicone iliac artery phantom using vessel loops. Two-dimensional digital subtraction angiographies (DSAs) were performed, with velocities calculated using qDSA. qDSA velocities were compared with flow rates and velocities measured with an ultrasonic flow probe. Two-dimensional DSAs of the common and external iliac arteries were then performed in 4 swine (mean weight, 63 kg) before and after a severe stenosis (>70%) was created in the iliac artery using 3-0 silk suture. Peak systolic velocities on pulsed wave Doppler ultrasound (US) before and after stenosis creation were correlated with the qDSA velocities. Pearson correlation, linear regression, and analysis of variance were used for analysis. RESULTS: In the phantom study, ultrasonic probe velocities positively correlated with downstream qDSA (r = 0.65; P < .001) and negatively correlated with peristenotic qDSA velocities (r = -0.80; P < .001). In the swine study, statistically significant reductions in external iliac arterial velocity were noted on US and qDSA after stenosis creation (P < .05). US and qDSA velocities strongly correlated for all flow states with both 50% and 100% contrast concentrations (r = 0.82 and r = 0.74, respectively), with an estimated US-to-qDSA ratio of 1.3-1.5 (P < .001). qDSA velocities with 50% and 100% contrast concentrations also strongly correlated (r = 0.78; P < .001). CONCLUSIONS: In both phantom and swine stenosis models, changes in iliac arterial velocity could be quantified with qDSA, which strongly correlated with standard-of-care US.

Reengaging patients with forgotten filters through an institutional multidisciplinary approach.

OBJECTIVE: The aim of the present study was to evaluate the outcomes of a hospital-wide multidisciplinary initiative to reengage and manage patients with unretrieved chronic indwelling inferior vena cava (IVC) filters placed at a large tertiary care center, who had been lost to follow-up. METHODS: We performed a retrospective review of outcomes from a completed multidisciplinary quality improvement project. The quality improvement project identified and contacted (via letter) patients with chronic indwelling IVC filters placed at a single tertiary care center from 2008 to 2016 who were alive and without evidence of filter retrieval in the medical records. A total of 316 eligible patients were mailed a letter regarding their chronic indwelling IVC filter and the updated recommendations regarding IVC filter removal. The letter included institutional contact information, and all the patients who responded were offered a clinic visit to discuss potential filter retrieval. In the retrospective review, we assessed the outcomes of the quality improvement project, including the patient response rate, follow-up clinic visits, new imaging studies generated, retrieval rate, procedural success, and complications. The patient demographics and filter characteristics were collected and evaluated for correlations with the response and retrieval rates. RESULTS: The patient response rate to the letter was 32% (101 of 316). Of the 101 patients who responded, 72 (71%) were seen in clinic and 59 (82%) underwent new imaging studies. Using standard and advanced techniques, 34 of 36 filters after a median dwell time of 9.4 years (range, 3.3-13.3 years) were successfully retrieved (94% success rate). The patients with a documented IVC filter complication were more likely to respond to the letter (odds ratio, 4.34) and undergo IVC filter retrieval (odds ratio, 6.04). No moderate or severe procedural complications occurred during filter retrieval. CONCLUSIONS: An institutional, multidisciplinary quality initiative successfully identified and reengaged patients with chronic indwelling IVC filters who had been lost to follow-up. The filter retrieval success rate was high and procedural morbidity low. Institution-wide efforts to identify and retrieve chronic indwelling filters are feasible.

Radioembolization Followed by Transarterial Chemoembolization in Hepatocellular Carcinoma.

BACKGROUND AND OBJECTIVE: In recent years, combination therapies for hepatocellular carcinoma (HCC) have been increasingly used with superior treatment responses compared to monotherapies. However, the safety and efficacy of the transarterial chemoembolization (TACE) and transarterial radioembolization (TARE) combinations for HCC patients have not been investigated in the literature. In this study, our aim was to evaluate the safety and outcomes of TACE after TARE in HCC patients. MATERIALS AND METHODS: All TARE procedures performed on HCC patients at a single institution between January 2008 and November 2016 were retrospectively reviewed. Seventy-three patients who did not receive any additional transarterial therapy in the areas targeted by TARE were assigned to the "TARE group," while 27 patients who received TACE after TARE to the same target area were assigned to the "Combo group." Post-procedural liver toxicity, tumor response, overall survival (OS), and time to progression (TTP) were evaluated. RESULTS: Fewer patients in the Combo group had worsening liver function than the TARE group based on the change in bilirubin levels (19% vs. 40%; p=0.029) and Child-Pugh score increase (28% vs. 51%; p=0.056). The median OS time of all patients was 11.04 months. The Combo group had a significantly longer median OS of 36.8 months (vs. 10.6, p=0.003) and median TTP of 14.4 months (vs. 5.5, p=0.018). After accounting for selection bias, OS and TTP were still in favor of the Combo group, with hazard ratios of 0.651 (p<0.05) and 0.63 (p<0.05), respectively. CONCLUSION: The addition of TACE to TARE is a safe and effective treatment in unresectable HCC patients and can be considered in select patients with a lack of complete response or disease progression.

Evaluation of staging systems to predict prognosis in hepatocellular carcinoma patients treated with radioembolization.

PURPOSE: To compare the prognostic accuracy of nine staging systems, some of which are well-known and some of which have only been more recently described, for patients with unresectable HCC treated with radioembolization (RE). MATERIALS AND METHODS: Individual scores or classes for the following staging systems were recorded or calculated for patients (n = 89) with unresectable HCC who underwent RE at a single tertiary care center from January 2008 to October 2016: Eastern Cooperative Oncology Group, Barcelona Clinic Liver Cancer, Hong Kong Liver Cancer, Okuda, Cancer of the Liver Italian Program (CLIP), Model for End Stage Liver Disease, Child-Pugh (CP) Categorical and Numeric, and Albumin-Bilirubin. For each staging system, a cox proportional hazards regression model was fit to the data and log-rank test statistics, concordance indices, Akaike Information Criteria (AIC) and other diagnostic statistics were calculated. RESULTS: Of the nine staging systems analyzed, the basic discriminatory ability assessed with the log-rank test (rejected at the α = .05-level) was significant for two of the systems: CP Numeric (p < .001) and CLIP (p < .05). Out of these two systems, CP Numeric system had a higher prognostic accuracy than CLIP with the lowest AIC (464.90), the highest optimism-corrected pseudo R2 (0.16), and the highest estimated concordance index (0.64). CONCLUSION: As applied to our patient population, the CP Numeric system contained the most predictive prognostic information for patients with HCC undergoing radioembolization. However, all evaluated staging systems performed suboptimally, and the relative superiority of any of the systems remains unclear when ranking them according to common practice. Further evaluation of current ranking methodologies is recommended.

Diagnostic Accuracy and Failure Mode Analysis of a Deep Learning Algorithm for the Detection of Intracranial Hemorrhage.

OBJECTIVE: To determine the institutional diagnostic accuracy of an artificial intelligence (AI) decision support systems (DSS), Aidoc, in diagnosing intracranial hemorrhage (ICH) on noncontrast head CTs and to assess the potential generalizability of an AI DSS. METHODS: This retrospective study included 3,605 consecutive, emergent, adult noncontrast head CT scans performed between July 1, 2019, and December 30, 2019, at our institution (51% female subjects, mean age of 61 ± 21 years). Each scan was evaluated for ICH by both a certificate of added qualification certified neuroradiologist and Aidoc. We determined the diagnostic accuracy of the AI model and performed a failure mode analysis with quantitative CT radiomic image characterization. RESULTS: Of the 3,605 scans, 349 cases of ICH (9.7% of studies) were identified. The neuroradiologist and Aidoc interpretations were concordant in 96.9% of cases and the overall sensitivity, specificity, positive predictive value, and negative predictive value were 92.3%, 97.7%, 81.3%, and 99.2%, respectively, with positive predictive values unexpectedly lower than in previously reported studies. Prior neurosurgery, type of ICH, and number of ICHs were significantly associated with decreased model performance. Quantitative image characterization with CT radiomics failed to reveal significant differences between concordant and discordant studies. DISCUSSION: This study revealed decreased diagnostic accuracy of an AI DSS at our institution. Despite extensive evaluation, we were unable to identify the source of this discrepancy, raising concerns about the generalizability of these tools with indeterminate failure modes. These results further highlight the need for standardized study design to allow for rigorous and reproducible site-to-site comparison of emerging deep learning technologies.

Optimization of quantitative time-resolved 3D (4D) digital subtraction angiography in a porcine liver model.

BACKGROUND: Time-resolved three-dimensional digital subtraction angiography (4D-DSA) can be used to quantify blood velocity. Contrast pulsatility, a major discriminant on 4D-DSA, is yet to be optimized. We investigated the effects of different imaging and injection parameters on sideband ratio (SBR), a measure of contrast pulsatile strength, within the hepatic vasculature of an in vivo porcine model. METHODS: Fifty-nine hepatic 4D-DSA procedures were performed in three female domestic swine (mean weight 54 kg). Contrast injections were performed in the common hepatic artery with different combinations of imaging duration (6 s or 12 s), injection rates (from 1.0 to 2.5 mL/s), contrast concentration (50% or 100%), and catheter size (4 Fr or 5 Fr). Reflux was recorded. SBR and vessel cross-sectional areas were calculated in 289 arterial segments. Multiple linear mixed-effects models were estimated to determine the effects of parameters on SBR and cross-sectional vessel area. RESULTS: Twelve-second acquisitions yielded a SBR higher than 6 s (p < 0.001). No significant differences in SBR were seen between different catheter sizes (p = 0.063) or contrast concentration (p = 0.907). For higher injection rates (2.5 mL/s), SBR was lower (p = 0.007) and cross-sectional area was higher (p < 0.001). Reflux of contrast does not significantly affect SBR (p = 0.087). CONCLUSIONS: The strength of contrast pulsatility used for flow quantitation with 4D-DSA can be increased by adjusting injection rates and using longer acquisition times. Reduction of contrast concentration to 50% is feasible and reflux of contrast does not significantly hinder contrast pulsatility.

Quantitative 4D-Digital Subtraction Angiography to Assess Changes in Hepatic Arterial Flow during Transarterial Embolization: A Feasibility Study in a Swine Model.

PURPOSE: To determine the feasibility of using time-resolved 3D-digital subtraction angiography (4D-DSA) for quantifying changes in hepatic arterial blood flow and velocity during transarterial embolization. MATERIALS AND METHODS: Hepatic arteriography and selective transarterial embolization were performed in 4 female domestic swine (mean weight, 54 kg) using 100-300-µm microspheres. Conventional 2D and 4D-DSA were performed before, during, and after each embolization. From the 4D-DSA reconstructions, blood flow and velocity values were calculated for hepatic arterial branches using a pulsatility-based algorithm. 4D-DSA velocity values were compared to those measured using an intravascular Doppler wire with a linear regression analysis. Paired t-tests were used to compare data before and after embolization. RESULTS: There was a weak-to-moderate but statistically significant correlation of flow velocities measured with 4D-DSA and the Doppler wire (r = 0.35, n = 39, P = .012). For vessels with high pulsatility, the correlation was higher (r = 0.64, n = 11, P = .034), and the relationship between 4D-DSA and the Doppler wire fit a linear model with a positive bias toward the Doppler wire (failed to reject at 95% confidence level, P = .208). 4D-DSA performed after partial embolization showed a reduction in velocity in the embolized hepatic arteries compared to pre-embolization (mean, 3.96 ± 0.74 vs 11.8 2± 2.15 cm/s, P = .006). CONCLUSION: Quantitative 4D-DSA can depict changes in hepatic arterial blood velocity during transarterial embolization in a swine model. Further work is needed to optimize 4D-DSA acquisitions and to investigate its applicability in humans.

Comparison of Conventional and Cone-Beam CT for Monitoring and Assessing Pulmonary Microwave Ablation in a Porcine Model.

PURPOSE: To compare cone-beam computed tomography (CT) with conventional CT for assessing the growth and postprocedural appearance of pulmonary microwave ablation zones. MATERIALS AND METHODS: A total of 17 microwave ablations were performed in porcine lung in vivo by applying 65 W for 5 minutes through a single 17-gauge antenna. Either CT (n = 8) or CBCT (n = 9) was used for guidance and ablation zone monitoring at 1-minute intervals. Postprocedural noncontrast images were acquired with both modalities. Three independent readers measured the length, width, cross-sectional area, and circularity of the ablation zones on gross tissue samples and CT and cone-beam CT images. The measurements were compared via linear mixed-effects models for postprocedural appearance and with a polynomial mixed effects model for ablation zone growth curves. RESULTS: On postprocedural images, the differences between cone-beam CT and CT in mean length (3.84 vs 3.86 cm; Δ = -0.02; P = .70), width (2.61 vs 2.56 cm; Δ = 0.06; P = .46), area (7.84 vs 7.65 cm2; Δ = 0.19; P = .35), and circularity (0.85 vs 0.85; Δ = 0.01; P = .62) were not statistically significant after accounting for intersubject and interrater variability. Also, there was no significant difference between CT and cone-beam CT growth curves of the ablation zones during monitoring in terms of length (pInt. = 1.00; pLin.Slope = 0.52; pQuad.Slope = 0.69); width (pInt. = 0.83; pLin.Slope = 0.98; pQuad.Slope = 0.79), area (pInt. = 0.47; pLin.Slope = 0.27; pQuad.Slope = 0.57), or circularity (pInt. = 0.54; pLin.Slope = 0.74; pQuad.Slope = 0.80). Both CT and cone-beam CT overestimated gross pathologic observations of ablation length, width, and area (P < .001 for all). CONCLUSIONS: Cone-beam CT was similar to conventional CT when assessing the growth, final size, and shape of pulmonary microwave ablation zones and may be useful for monitoring and evaluating microwave ablations in the lung.

Benign Malformative Lesion of the Skull: Hamartoma with Ectopic Elements or Choristoma?

Hamartoma and choristoma are terms that describe non-neoplastic, mass-forming malformative lesions. Although each lesion has a different composition, they have been used interchangeably in many reports, especially for malformative lesions containing ectopic or heterologous elements. We report a three month-old girl who was brought to the clinic with a mass lesion at the posterior fontanel, composed of predominantly osteo-cartilaginous tissue admixed with skeletal muscle, peripheral nerve tissue, and ganglion. The mass was resected completely. The composition of this benign lesion with ectopic elements was consistent with an osteo-cartilaginous hamartoma. We discuss the biological and clinical aspects such malformative lesions within the skull to highlight the inconsistencies of the nomenclature used in the literature.

Crimean-Congo hemorrhagic fever infections reported by ProMED.

OBJECTIVE: There are limited sources describing the global burden of emerging diseases. We reviewed the Crimean-Congo hemorrhagic fever virus (CCHFV) infections reported by ProMED and assessed the reliability of the data retrieved compared to published reports. We evaluated the effectiveness of ProMED as a source of epidemiological data by focusing on CCHFV infections. METHODS: Using the keywords "Crimean Congo hemorrhagic fever" and "Crimean Congo" in the ProMED search engine, we reviewed all the information about the news and harvested data using a structured form, including year, country, gender, occupation, the number of infected individuals, and the number of fatal cases. RESULTS: We identified 383 entries reported between January 1998 and October 2013. A total 3426 infected cases were reported, with 451 fatal cases, giving an overall case fatality rate (CFR) of 13%. Out of 144 cases for which the gender was reported, 97 (67%) were male. Most of the cases were reported from Turkey, followed by Russia, Iran, Pakistan, and Afghanistan. CONCLUSIONS: Case reporting systems such as ProMED are useful to gather information and synthesize knowledge on the emerging infections. Although certain areas need to be improved, ProMED provided good information about Crimean-Congo hemorrhagic fever.

Shear stress-induced improvement of red blood cell deformability.

Classically, it is known that red blood cell (RBC) deformability is determined by the geometric and material properties of these cells. Experimental evidence accumulated during the last decade has introduced the concept of active regulation of RBC deformability. This regulation is mainly related to altered associations between membrane skeletal proteins and integral proteins, with the latter serving to anchor the skeleton to the lipid matrix. It has been hypothesized that shear stress induces alterations of RBC deformability: the current study investigated the dynamics of the transient improvement in deformability induced by shear stress at physiologically-relevant levels. RBC were exposed to various levels of shear stress (SS) in a Couette type shearing system that is part of an ektacytometer, thus permitting the changes in RBC deformability during the application of SS to be monitored. Initial studies showed that there is an increase in deformability of the RBC subjected to SS in the range of 5-20 Pa, with kinetics characterized by time constants of a few seconds. Such improvement in deformability, expressed by an elongation index (EI), was faster with higher levels of SS and hence yielded shorter time constants: absolute values of EI increased by 3-8% of the starting level. Upon the removal of the shear stress, this response by RBC was reversible with a slower time course compared to the increase in EI during application of SS. Increased calcium concentration in the RBC suspending medium prevented the improvement of deformability. It is suggested that the improvement of RBC deformability by shear forces may have significant effects on blood flow dynamics, at least in tissues supplied by blood vessels with impaired vasomotor reserve, and may therefore serve as a compensating mechanism for the maintenance of adequate microcirculatory perfusion.